1. Field of the Invention
The present invention relates to improved economical methods of forming one or more impermeable solid plugs in well bores.
2. Description of the Prior Art
When an oil, gas, water or other type of well penetrating one or more subterranean formations is a dry hole, has been depleted or is otherwise abandoned, the well bore must be plugged. The conventional technique for plugging a well bore has heretofore been to spot plugs of a hydraulic cement mixture at various levels in the well. The depths and compressive strengths of the cement plugs are typically specified by local governing regulatory agencies. Generally, a plug will be spotted and allowed to set at or near the bottom of the well bore with additional plugs spotted on top of mechanical plugs or bridging device at various levels and allowed to set.
The setting of mechanical plugs or bridging devices and the spotting of cement compositions onto the mechanical devices by pumping the cement compositions through work strings or the like as has heretofore been required is relatively time consuming and expensive.
Thus, there are needs for improved methods of forming plugs in well bores which are simple to carry out and relatively inexpensive.
The present invention provides improved methods of forming one or more plugs in abandoned well bores which meet the needs described above and overcome the deficiencies of the prior art. The methods of the present invention basically comprise the following steps. A cementitious material which will delayedly react with water to form an impermeable solid and which has been formed into agglomerates of sufficient weight to sink through the water and other fluids and materials in a well bore to be plugged are dropped into the well bore. The cementitious material agglomerates are dropped in a quantity sufficient to form a mass of the agglomerates adjacent to the natural bottom of the well bore. Thereafter, the mass of the cementitious material agglomerates is allowed to react with the water in the well bore to thereby form an impermeable solid plug therein.
When a plug must be placed above the natural bottom or above a first plug on the natural bottom of the well bore, one or more artificial bottoms are formed above the natural bottom or the first plug. A preferred simple and economical technique for forming an artificial bottom in the well bore in accordance with this invention is to pour sand into the well bore to fill the well bore to the level at which a plug is required to be formed. Thereafter, the cementitious material agglomerates of this invention are dropped into the well bore in a quantity sufficient to form a mass of the agglomerates therein. The agglomerates are then allowed to react with water in the well bore so that an impermeable solid plug is formed therein. If the formation of an artificial bottom utilizing sand or other similar relatively inexpensive material is impractical, a mechanical plug or bridging device can be utilized.
The cementitious material utilized can be a material which hydrates or otherwise reacts in the presence of water to form an impermeable solid mass in a well bore. The cementitious material can be formed into agglomerates in any convenient way such as by compacting the material, extruding the material or pelletizing the material whereby when the agglomerates are contacted with water they readily break apart and react with the water.
It is, therefore, a general object of the present invention to provide improved methods of forming plugs in abandoned well bores.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.